Source: Adapted from Family Medical Adviser, Reader’s Digest
What is pregnancy?
For conception to occur naturally, a woman needs to be ovulating – releasing an egg from one of her ovaries – which happens around the middle of each menstrual cycle. And her partner needs to be producing an adequate quantity of sperm.
During the first week or so after menstruation, there is a slow increase in levels of estrogen and follicle stimulating hormone (FSH). This initiates the growth of an egg within one of the ovaries and prompts changes to the uterine lining, making it thicker and spongy with blood, so that it is ready to receive a fertilized egg. Roughly two weeks after the beginning of a woman’s last period, an egg is released from one of her ovaries and ‘caught’ by the frilled membranes at the end of each fallopian tube. The cilia, tiny grass-like fronds that line the tubes, gently ease the egg towards the womb and the possibility of fertilization. If sex takes place around the time of ovulation, conception can occur.
Around 300 million sperm are released during sexual intercourse, but only a few hundred ever reach the fallopian tube that contains an egg. Sperm that do reach an egg release enzymes that slowly soften and break down the protective layer of cells surrounding the egg (corona radiata), until one finally breaks through. The moment a sperm reaches the surface of the egg the two cells – one from the sperm and one from the egg – merge. This merged cell forms a tough outer surface that repels any remaining sperm.
When is pregnancy possible?
There are probably no more than 100 days in a year when a woman of childbearing age is likely to conceive, and fewer days of peak fertility.
Some women have an intuitive feeling that they are pregnant even before they have missed a period, although many women have no sign at all.
You can test whether you are pregnant with a pregnancy testing kit. Most kits are so sensitive that they can confirm a pregnancy if your period is only one day late. Over-the-counter pregnancy tests work by measuring a hormone called human chorionic gonadotrophin (HCG). Kits consist of a small plastic stick containing a panel that reacts to HCG. This is dipped into a urine sample taken first thing in the morning; if HCG is present, the reactive panel changes colour in a few minutes. If there is no reaction within 15 minutes, pregnancy is unlikely. But home pregnancy tests are not infallible. A false positive result can be caused by hormones administered for fertility treatment, and by a recent miscarriage or pregnancy. Detergent in the container used to collect urine, or a test taken too early, when HCG is still very low, and some drugs including tranquillizers and antihistamines, may give a false negative result.
Women often do not realize that they have conceived until around the eighth week of pregnancy, when they know they have missed a period. By now, most of the baby’s organs are developing, so it is wise to adopt a healthy lifestyle and diet before trying to conceive. It is usually safe to work throughout pregnancy, and many women choose to work right up until the birth.
Keeping fit is an important part of a healthy pregnancy, and low-impact exercise such as swimming, walking and yoga are excellent.
Here are some guidelines that will help you give your baby the best possible start:
- Take 400mcg folic acid each day for the first three months of pregnancy. This will reduce your baby’s risk of neural tube defects such as spina bifida and other problems including cleft palate. Ideally, you should take folic acid before pregnancy too, so begin a course of tablets as soon as you decide to try for a baby.
- Make sure that your diet includes plenty of B group vitamins – thiamin, niacin, riboflavin and B6 – to cut the risk of a low-birthweight baby.
- Avoid soft and unpasteurized cheeses, raw eggs and raw or undercooked meats; they could carry salmonella, listeria and other bacterial infections.
- It is best to avoid alcohol during pregnancy. The safe level is not known, and individual tolerance varies. Alcohol abuse can cause fetal alcohol syndrome, resulting in low birthweight and mental retardation.
- Don’t smoke. Smoking increases the risk of miscarriage and having a low-birthweight baby.
- Avoid liver and liver pâté: liver is high in retinol, the form of vitamin A found in animal products, which has been linked to birth defects. If you are taking a multivitamin or supplement, look for one that contains vitamin A in the form of beta carotene and has no more than 1250mcg.
- Avoid touching pregnant livestock; they may carry bacteria that cause miscarriage.
- Avoid exposure to X-rays and anaesthetic gases.
- Be wary of toxoplasmosis, a parasitic infection that causes miscarriage and stillbirth. It can be picked up by eating raw or undercooked meat, or from animals.
- Avoid saunas and extremely high temperatures.
If you’re pregnant, you will have to keep in mind that everything you do and don’t do affects your baby.
The fetus is completely dependent on its mother for nourishment and oxygen, both of which pass from mother to baby via the placenta. Every minute, about 600ml (just over a pint) of blood flows from the mother to her baby through the placenta. This carries oxygen and nutrients to the baby and removes waste products, which are then processed and eliminated by the mother’s body.